# # Program information file # PROGRAM_ID 2022A044 PROGRAM_TITLE Characterizing the Variable Debris Disk Around HD 166191 PROGRAM_INV1 Kate Su PROGRAM_INV2 George Rieke PROGRAM_INV3 Michael Sitko PROGRAM_INV4 Taran Esplin PROGRAM_INV5 PROGRAM_SCICAT extra-solar planets PROGRAM_ABSTRACT_BEG Variable debris disks, discovered by Spitzer, give new insights into the collisional processes between planetary embryos and oligarchs in the terrestrial planet region over a period of about 200 Myr after protoplanetary disks have cleared. They have let us set timescales for the clearing of collisional debris, critical to understand the duty cycle of infrared excesses and the incidence of major planetesimal collisions by monitoring the orbital evolution of the initially optically thick clouds released in collisions. The majority of such varable systems monitored by the warm Spitzer [ended in early 2020] are too faint to follow up with ground-based telescopes. However, one system, HD 166191, has recently undergone a major series of collisions and is bright enough to monitor from the ground. Existing IRTF observations obtained in 2020/2021 have shown that ~5-30% disk variability in timescales of a few weeks is detectable with IRTF/SpeX [similar to the quality of warm Spitzer data]. We propose to continue monitoring the system in 2022A using SpeX and MIRSI. The proposed IRTF observations would provide valuable information on how the system evolves during the observing gap between Spitzer and future facilities like SOFIA and JWST, and be part of the important NASA legacy on characterizing this unique system. PROGRAM_ABSTRACT_END